This multidisciplinary project was designed, primarily, to study the effect of a rapidly changing environment on the transmission dynamics of arboviruses in a tropical forest area. The rapid changes in the environment are to be caused by construction of a hydroelectric dam across the Bayano river, in eastern Panama province. Target date for impoundment has now been set for January, 1975. At present base-line data are being gathered on microclimatic factors, population dynamics of vectors and hosts and existing arbovirus transmission chains. All data gathered are being processed through a central computer program in a manner that will permit correlation of all pieces of information gathered in the different ecological aspects being studied. As impoundment occurs and a lake with an area of 300 Km2 is formed, the study site will become an island in the lake, from where the impact of the changes, produced during and after the impoundment, on the population dynamics of vectors and hosts of disease and on arbovirus transmission cycles may be studied. It is hoped that results obtained by these studies may produce a basis for predicting effects of similar projects on the general ecology of affected areas in tropical America.